Polymer blend and fabricated article made from diverse ethylene interpolymers

ABSTRACT

This invention is directed to an ethylene polymer blend comprising at least two diverse ethylene interpolymers wherein one interpolymer has a lower number of carbons than the at least one other interpolymer. The ethylene polymer blend preferably comprises at least one homogeneously branched ethylene/α-olefin interpolymer blended with at least one heterogeneously branched ethylene/α-olefin interpolymer and is characterized as having a density greater than or equal to 0.90 g/cm 3  and in particularly preferred embodiments is further characterized as having an intrinsic tear value greater than or equal to 150 grams. The inventive ethylene polymer blend can be used to make various fabricated articles, especially extruded forms and most especially films such as high strength thin gauge packaging film, impact resistant shrink film and heat sealable packaging film.

FIELD OF THE INVENTION

[0001] This invention relates to an ethylene polymer blend comprising atleast two diverse ethylene interpolymers wherein one interpolymer has alower number of carbons than the at least one other interpolymer. Theethylene polymer blend preferably comprises at least one homogeneouslybranched ethylene/α-olefin interpolymer blended with at least oneheterogeneously branched ethylene/α-olefin interpolymer and ischaracterized as having a density greater than or equal to 0.90 g/cm³and an intrinsic tear value greater than or equal to 150 grams-force.

[0002] The inventive ethylene polymer blend can be used in variousextruded forms and is particularly useful for film applications (forexample, high strength thin gauge packaging film, impact resistantshrink film and heat sealable packaging film).

BACKGROUND OF THE INVENTION

[0003] Film products fabricated from linear low density polyethylene(LLDPE) or high density polyethylene (HDPE) are widely used forpackaging applications such as merchandise bags, shrink films, grocerysacks, and industrial liners. For these applications, films withexcellent toughness properties (that is, high tensile, impact or tearstrengths) are desired to facilitate down gauging, prevent prematurepunctures during handling, distribution and use.

[0004] Previous attempts were made to optimize film tensile strength andyield strength by blending various heterogeneous polymers together ontheoretical basis. While such blends exhibited a synergistic response toincrease the film yield strength, the film impact strength followed therule of mixing, often resulting in a “destructive synergism” (that is,the film impact strength was actually lower than film made from one ofthe two components used to make the blend).

[0005] For example, it is known that while improved modulus linearpolyethylene polymer blends can be produced by blending high densitypolyethylene with a very low density polyethylene (VLDPE), the impactstrength of these polymer blends typically follow the rule of mixing (orthe “blend rule”). That is, the final composition exhibits propertiesthat are comparable to and predictable from weight average calculationsbased on the component polymers. For example, see FIG. 5 herein.

[0006] It is also known from U.S. Pat. No. 5,677,383, the disclosure ofwhich is incorporated herein by reference, that dramatic synergismresults when polymer compositions are made from a homogeneously branchedethylene interpolymer having a high slope of strain hardeningcoefficient melt-blended with a heterogeneously branched ethylenepolymer. Although U.S. Pat. No. 5,677,383 broadly discloses thehomogeneously branched ethylene interpolymer and the heterogeneouslybranched ethylene polymer can comprise various comonomers, all of thepresented examples consist of higher alpha olefin interpolymercombinations. Moreover, U.S. Pat. No. 5,677,383 focuses on the slope ofstrain hardening coefficient of the component polymers and is notdirected to the slope of strain hardening coefficient of the final blendcombinations.

[0007] It is also known that, at the equivalent densities, interpolymerscomprised of higher alpha olefins provide improved toughness propertiesas compared to lower alpha olefin interpolymers. For example, at adensity of about 0.935 g/cc, an ethylene/1-octene copolymer will exhibitan intrinsic tear that is about two times higher than that of anethylene/1-butene copolymer having about the same density.

[0008] It is well established that higher alpha olefin interpolymersprovide superior toughness. But with periodic scarcities in theavailability of higher alpha olefin comonomers, resin producers andfabricators desire broader polymer options for providing polymercompositions characterized by excellent toughness properties. The needis especially great in regard to 1-octene, which is a higher alphaolefin that frequently tends to be in short supply while the lower alphaolefin 1-butene generally tends to be abundantly available. For polymerblends comprising at least two higher alpha olefin interpolymers, thereis a particular need to substitute at least one of the higher alphaolefin interpolymers with a lower alpha olefin interpolymer and stillretain the excellent toughness properties characteristic of higher alphaolefin polymer blends. For polymer blends comprising at least two higheralpha olefin interpolymers where one is a homogeneously branchedethylene interpolymer and the other is a heterogeneously branchedethylene polymer, there is an especially particular need to substituteat least one of the higher alpha olefin interpolymers with a lower alphaolefin interpolymer and still retain the excellent toughness propertiescharacteristic of these polymer blends.

[0009] Surprisingly, we have now discovered that within a certain narrowdensity range, tailored combinations of at least one interpolymercomprised of a lower carbon comonomer blended with at least oneinterpolymer comprised of a higher carbon comonomer can providetoughness properties comparable to polymer blends comprised of twointerpolymers, each having the same higher carbon comonomer or,alternatively, comparable to single interpolymer compositions where theinterpolymer comprises a higher carbon comonomer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1A and 1B are diagrams of test dogbones used for determiningthe slope of strain hardening coefficient.

[0011]FIG. 2 shows the various regions of a typical tensile curve (asload in pounds versus extension in inches) and the particular regionused to determine the slope of strain hardening.

[0012]FIG. 3 shows the relationship between intrinsic tear (in grams)and the slope of strain hardening coefficient (SHC) for twohomogeneously branched ethylene/1-octene copolymers and oneheterogeneously branched ethylene/1-octene copolymer.

[0013]FIG. 4 shows the relationship between intrinsic tear (in grams)and the overall density (in grams per cubic centimeter) for varioussingle polymer and polymer blend compositions, including inventiveinterpolymer combinations.

[0014]FIG. 5 shows, in regard to intrinsic tear (in grams), howdissimilar and similar interpolymer combinations compare to a “mixingrule” polymer blend of a homogeneously branched ethylene/1-butenecopolymer (having a 0.8714 g/cc density) and heterogeneously branchedethylene/1-octene copolymer (having a 0.934 g/cc density).

[0015]FIG. 6 shows, in regard to intrinsic tear (in grams), howdissimilar and similar interpolymer combinations compare to a “mixingrule” polymer blend of a homogeneously branched ethylene/1-octenecopolymer (having a 0.8688 g/cc density) and heterogeneously branchedethylene/1-octene copolymer (having a 0.934 g/cc density).

[0016]FIG. 7 shows, in regard to intrinsic tear (in grams), howdissimilar and similar interpolymer combinations compare to a “mixingrule” polymer blend of a homogeneously branched ethylene/1-octenecopolymer (having a 0.909 g/cc density) and heterogeneously branchedethylene/1-butene copolymer (having a 0.936 g/cc density).

[0017]FIG. 8 shows, in regard to intrinsic tear (in grams), howdissimilar and similar interpolymer combinations compare to a “mixingrule” polymer blend of a homogeneously branched ethylene/1-octenecopolymer (having a 0.909 g/cc density) and heterogeneously branchedethylene/1-octene copolymer (having a 0.935 g/cc density).

[0018]FIG. 9 shows, in regard to intrinsic tear (in grams), howdissimilar and similar interpolymer combinations compare to a “mixingrule” polymer blend of a homogeneously branched ethylene/1-octenecopolymer (having a 0.8714 g/cc density) and heterogeneously branchedethylene/1-octene copolymer (having a 0.920 g/cc density).

SUMMARY OF THE INVENTION

[0019] Formulated ethylene interpolymer compositions comprised ofdissimilar interpolymers where at least one interpolymer comprises alower carbon comonomer relative to the other interpolymer (orinterpolymers), have now been discovered to have improved physical andmechanical strength and are useful in making fabricated articles. Thesenovel compositions exhibit surprisingly good toughness properties whichare comparable to synergistic interpolymer compositions comprised of twointerpolymers, each having the same higher carbon comonomer; orcomparable to “mixing rule” polymer blends comprised two interpolymers,each having the same higher carbon comonomer; or comparable to singlepolymer compositions comprised higher carbon comonomers.

[0020] The broad aspect of the invention is a diverse interpolymercomposition comprising

[0021] (A) from about 5 percent (by weight of the total composition) toabout 95 percent (by weight of the total composition) of at least onefirst ethylene interpolymer, and

[0022] (B) from about 95 percent (by weight of the total composition) toabout 5 percent (by weight of the total composition) of at least onesecond ethylene interpolymer;

[0023] wherein the first interpolymer is characterized as comprising adifferent comonomer relative to the second interpolymer, oneinterpolymer is a homogeneously branched ethylene interpolymer and theother interpolymer is a heterogeneously branched ethylene interpolymeror a homogeneously branched ethylene interpolymer, and the compositionis characterized as having a density greater than or equal to 0.90g/cm³.

[0024] In another aspect, the diverse interpolymer composition comprises

[0025] (A) from about 5 percent (by weight of the total composition) toabout 95 percent (by weight of the total composition) of at least onefirst ethylene interpolymer, and

[0026] (B) from about 95 percent (by weight of the total composition) toabout 5 percent (by weight of the total composition) of at least onesecond ethylene interpolymer;

[0027] wherein the first interpolymer is characterized as comprising adifferent comonomer relative to the second interpolymer and as having alower density relative to the second interpolymer; the secondinterpolymer is characterized as having a density less than or equal to0.95 g/cm3;

[0028] wherein one interpolymer is a homogeneously branched ethyleneinterpolymer and the other interpolymer is a heterogeneously branchedethylene interpolymer or a homogeneously branched ethylene interpolymer;and

[0029] wherein the composition is characterized as having a density inthe range of from greater than or equal to 0.90 g/cc to about 0.935g/cc.

[0030] In certain preferred embodiments of the present invention,preferably, at least the first interpolymer or the second interpolymeror both have a slope of strain hardening coefficient greater than orequal to 1.3, more preferably greater than or equal to 1.5. In otherpreferred embodiments, the diverse interpolymer composition has anintrinsic tear value greater than or equal to 150 grams, preferablygreater than or equal to 200 grams, more preferably greater than orequal 225 grams, or a slope of strain hardening coefficient greater thanor equal to 0.85, preferably greater than or equal to 0.95, morepreferably greater than or equal to 1.

[0031] In still other preferred embodiments, especially when balancedproperties are desired, the first interpolymer comprises a lower carboncomonomer. More preferably, the first interpolymer comprises a lowercarbon comonomer and is a homogeneously branched ethylene interpolymer.Most preferably, the first interpolymer comprises a lower carboncomonomer and is a substantially linear ethylene interpolymer.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The term “lower carbon comonomer” is used herein in reference toa comonomer that has a lower total number of carbons relative to anothercomonomer. Similarly, the term “higher carbon comonomer” is used hereinin reference to a comonomer that has a higher total number of carbonsrelative to another comonomer. The term “higher carbon comonomer” is ageneric reference that embraces the term “higher α-olefin” and the term“lower carbon comonomer” is a generic term that embraces the term “lowerα-olefin”. Thus, for example, 1-octene is would be a higher carboncomonomer (as well as a higher α-olefin) relative to 1-butene and,conversely, 1-butene would be a lower carbon comonomer (as well as alower α-olefin) relative to 1-octene. Also, 1-octene would be a“different comonomer” (as this term is used herein) relative to1-butene.

[0033] By the term “comparable toughness properties” it is meant thatthe intrinsic tear of the inventive diverse interpolymer composition, asdetermined in accordance with ASTM D-1922, Method A), is within 35percent, preferably 25 percent, more preferably 12 percent of theintrinsic tear of a comparative “mixing rule” polymer blend wherein thecompared polymer blend is comprised two interpolymers, each having thesame higher carbon comonomer. Comparable intrinsic tear performance isconsidered to be a surprisingly substantial improvement becauseordinarily interpolymers comprised higher carbon comonomers are expectedto exhibit vastly superior toughness properties over interpolymers basedon lower carbon comonomer.

[0034] The term “mixing rule” as discussed above is used herein to referto polymer blend property results attainable from fractional weightaverage calculations based on the properties of the component polymersof the polymer blend.

[0035] The density of the inventive diverse interpolymer composition (asmeasured in accordance with ASTM D-792) is generally from greater thanor equal to 0.90 g/cm³. Preferably, in the range of from greater than orequal to 0.90 g/cm³ to about 0.935 g/cm³, more preferably from greaterthan or equal to 0.90 g/cm³ to less than or equal to 0.925 g/cm³, mostpreferably from about 0.905 g/cm³ to about 0.925 g/cm³, and especiallyfrom about 0.905 g/cm³ to than about 0.92 g/cm³.

[0036] The I₂ melt index of the inventive diverse interpolymercomposition is preferably in the range of from about 0.1 to about 100g/10 minutes, more preferably in the range of from about 0.2 to 10 g/10minutes, most preferably less than or equal to 2.5 g/10 minutes.

[0037] The inventive diverse interpolymer composition can be alternatelyor further characterized as having an intrinsic tear (as measured inaccordance with ASTM D-1922, Method A) preferably greater than or equalto 150 grams, more preferably greater than or equal to 200 grams andmost preferably greater than or equal to 225 grams, and especiallygreater than or equal to 250 grams.

[0038] Preferably, the carbon difference between the at least onecomonomer of the first interpolymer and the at least one comonomer ofthe second interpolymer is greater than 2, especially greater than orequal to 3, most especially greater than or equal to 4. Especiallypreferred are copolymer combinations (that is, each interpolymercomprises ethylene with only one other comonomer). More especiallypreferred are copolymer combinations comprising 1-octene (for examplecombinations of 1-octene with 1-pentene, 1-octene with 1-butene and1-octene with propylene). Most especially preferred are copolymercombinations comprising 1-octene and 1-butene (for example, asubstantially linear ethylene/1-octene copolymer blended with aheterogeneously branched ethylene/1-butene copolymer).

[0039] The homogeneously branched ethylene interpolymer is preferably asubstantially linear ethylene/α-olefin or diolefin interpolymer, asdescribed in U.S. Pat. No. 5,272,236 and U.S. Pat. No. 5,278,272, thedisclosures of both of which are incorporated herein by reference. Thehomogeneously branched ethylene interpolymer can also be a linearethylene interpolymer (that is, characterized as having no long chainbranching and certain less than 0.01 long chain branch per 1000 carbonatoms) as described, for example, in U.S. Pat. No. 3,645,992 (Elston),the disclosure of which is incorporated herein by reference.

[0040] Substantially linear ethylene interpolymers are not “linear”polymers in the traditional sense of the term and as used to describelinear low density polyethylene (for example, Ziegler polymerized linearlow density polyethylene (LLDPE)). Nor are substantially linear ethyleneinterpolymers highly branched polymers, as used to describe highpressure, free-radical initiated low density polyethylene (LDPE).

[0041] The homogeneously branched ethylene interpolymers useful forforming the diverse interpolymer composition described herein are thosein which the comonomer is randomly distributed within a giveninterpolymer molecule and wherein substantially all of the interpolymermolecules have the same ethylene/comonomer ratio within thatinterpolymer. The homogeneity of homogeneously branched ethyleneinterpolymers (either substantially linear ethylene interpolymers orhomogeneously branched linear ethylene interpolymers) is typicallydescribed by the SCBDI (Short Chain Branch Distribution Index) or CDBI(Composition Distribution Branch Index).

[0042] SCBDI is defined as the weight percent of the polymer moleculeshaving a comonomer content within 50 percent of the median total molarcomonomer content and represents a comparison of the comonomerdistribution in the interpolymer to the comonomer distribution expectedfor a Bernoullian distribution. The SCBDI of an interpolymer can bereadily calculated from TREF as described, for example, by Wild et al.,Journal of Polymer Science. Poly. Phys. Ed., Vol. 20, p. 441 (1982), orin U.S. Pat. 4,798,081; 5,008,204; or by L. D. Cady, “The Role ofComonomer Type and Distribution in LLDPE Product Performance,” SPERegional Technical Conference, Quaker Square Hilton, Akron, Ohio,October 1-2, pp.107-119 (1985), the disclosures of all which areincorporated herein by reference.

[0043] The preferred TREF technique does not include purge quantities inSCBDI calculations. More preferably, the comonomer distribution of theinterpolymer and SCBDI are determined using ¹³C NMR analysis inaccordance with techniques described in U.S. Pat. No. 5,292,845; U.S.Pat. No. 4,798,081; U.S. Pat. No. 5,089,321 and by J. C. Randall, Rev.Macromol. Chem. Phys., C29, pp. 201-317, the disclosures of all of whichare incorporated herein by reference.

[0044] In analytical temperature rising elution fractionation analysis(as described in U.S. Pat. No. 4,798,081 and abbreviated herein as“ATREF”), the film or composition to be analyzed is dissolved in asuitable hot solvent (e.g., trichlorobenzene) and allowed tocrystallized in a column containing an inert support (stainless steelshot) by slowly reducing the temperature. The column is equipped withboth a refractive index detector and a differential viscometer (DV)detector. An ATREF-DV chromatogram curve is then generated by elutingthe crystallized polymer sample from the column by slowly increasing thetemperature of the eluting solvent (trichlorobenzene). The ATREF curveis also frequently called the short chain branching distribution (SCBD),since it indicates how evenly the comonomer (e.g., octene) isdistributed throughout the sample in that as elution temperaturedecreases, comonomer content increases. The refractive index detectorprovides the short chain distribution information and the differentialviscometer detector provides an estimate of the viscosity averagemolecular weight. The short chain branching distribution and othercompositional information can also be determined using crystallizationanalysis fractionation such as the CRYSTAF fractionalysis packageavailable commercially from PolymerChar, Valencia, Spain.

[0045] The SCBDI for the homogeneously branched linear ethyleneinterpolymer and the substantially linear ethylene interpolymers used inthe present invention is preferably greater than 50 percent, especiallygreater than 70 percent and most especially greater than 90 percent.That is, by the term “homogeneously branched ethylene interpolymer” itis meant an ethylene interpolymer having a SCBDI greater than 50percent.

[0046] Preferred homogeneously branched ethylene interpolymers useful inthis invention also essentially lack a measurable “linear”, “highdensity” or “crystalline” polymer fraction as measured by the TREFtechnique (that is, preferred homogeneously branched ethyleneinterpolymers do not contain a polymer fraction with a degree ofbranching less than or equal to 2 methyls/1000 carbons). Morepreferably, the homogeneously branched ethylene interpolymers also donot contain any highly short chain branched fraction (that is, morepreferred homogeneously branched ethylene interpolymers do not contain apolymer fraction with a degree of branching equal to or more than about30 methyls/1000 carbons). Although suitable for use in the presentinvention and not the preferred (or more preferred), commercial examplesof homogeneously branched ethylene interpolymers having a “linear”,“high density” or “crystalline” polymer fraction include certain gradesof EXCEED resins supplied by Exxon Chemical Company.

[0047] The homogeneously branched ethylene interpolymers andheterogeneously branched ethylene interpolymers for use in the presentinvention typically are interpolymers of ethylene with at least oneC₃-C₂₀ α-olefin or C₄-C₁₈ diolefin. Copolymers of ethylene and 1-octeneare especially preferred. The term “interpolymer” is used herein toindicate a copolymer, or a terpolymer, or the like. That is, at leastone other comonomer is polymerized with ethylene to make theinterpolymer. Ethylene copolymerized with two or more comonomers canalso be used to make the homogeneously branched substantially linearinterpolymers useful in this invention. Preferred comonomers include theC₃-C₂₀ α-olefins, especially propylene, isobutylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and 1-decene, morepreferably 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene.

[0048] The term “linear ethylene interpolymer” means that theinterpolymer does not have long chain branching. That is, the linearethylene interpolymer has an absence of long chain branching. The term“linear ethylene interpolymer” does not refer to high pressure branched,free-radical initiated polyethylene (LDPE) which is known to thoseskilled in the art to have numerous long chain branches. The comonomerbranching distribution of homogeneously branched linear ethyleneinterpolymers is the same or substantially the same as that describedfor the substantially linear ethylene/interpolymers, with the exceptionthat the linear ethylene interpolymers do not have any long chainbranching.

[0049] Substantially linear ethylene interpolymers have a single meltingpoint, as opposed to traditional heterogeneously branched Zieglerpolymerized ethylene interpolymers which have two or more meltingpoints, as determined using differential scanning calorimetry (DSC).Most (but not all) homogeneously branched linear ethylene interpolymersalso have a single DSC melting point. Those homogeneously branchedlinear ethylene interpolymers that have a “linear”, “high density” or“crystalline” polymer fraction in TREF testing, generally have more thanone DSC melting point. Homogeneously branched ethylene polymers having asingle DSC melting point in the temperature range of −30° to 150° C. arepreferred for use in the present invention.

[0050] Preferably, the first interpolymer has a lower density than thesecond interpolymer. More preferably, the density of the firstinterpolymer, as measured in accordance with ASTM D-792, for use in thepresent invention is especially from about 0.89 g/cm³ to about 0.935g/cm³, more especially from about 0.90 g/cm³ to about 0.925 g/cm³, mostespecially from about 0.905 g/cm³ to about 0.925 g/cm³, and mostparticularly from about 0.905 g/cm³ to than about 0.92 g/cm³.

[0051] The amount of the first interpolymer and second interpolymerincorporated into the inventive diverse interpolymer composition variesdepending upon the desired melt index and targeted density of the finalcomposition. But preferably, the interpolymer composition comprises fromgreater than 20 weight percent to about 95 weight percent (based on thetotal weight of the composition) of the first interpolymer and from lessthan 80 weight percent to about 5 weight percent (based on the totalweight of the composition) of the second interpolymer. More preferably,the interpolymer composition comprises from greater than 25 weightpercent to about 85 weight percent (based on the total weight of thecomposition) of the first interpolymer and from less than 75 weightpercent to about 15 weight percent (based on the total weight of thecomposition) of the second interpolymer.

[0052] The molecular weight of the homogeneously branched ethyleneinterpolymer or the heterogeneously branched ethylene interpolymer foruse in the present invention is conveniently indicated using a meltindex measurement according to ASTM D-1238, Condition 190° C./2.16 kg(formerly known as “Condition (E)” and also known as I₂). Melt index isinversely proportional to the molecular weight of the polymer. Thus, thehigher the molecular weight, the lower the melt index, although therelationship is not linear. The lower melt index limit for the ethyleneinterpolymers useful herein is preferably about 0.001 grams/10 minutes(g/10 min). The upper melt index limit is preferably about 10 g/10 min,preferably less than about 1 g/10 min, and especially less than about0.5 g/10 min. Most preferably, the first interpolymer is a homogeneouslybranched ethylene interpolymer having an I₂ melt index equal to or lowerthan that of the second interpolymer which would be a heterogeneouslybranched ethylene interpolymer.

[0053] Another measurement useful in characterizing the molecular weightof the ethylene interpolymers is conveniently indicated using a meltindex measurement according to ASTM D-1238, Condition 190° C./10 kg(formerly known as “Condition (N)” and also known as I₁₀). The ratio ofthe I₁₀ and I₂ melt index terms is the melt flow ratio and is designatedas I₁₀/I₂.

[0054] Generally, the I₁₀/I₂ ratio for the homogeneously branched linearethylene interpolymers is about 5.6.

[0055] For the substantially linear ethylene interpolymers used in thecompositions of the invention, the I₁₀/I₂ ratio indicates the degree oflong chain branching; that is, the higher the I₁₀/I₂ ratio, the morelong chain branching in the interpolymer. Generally, the I₁₀/I₂ ratio ofthe branched substantially linear ethylene interpolymers is at leastabout 6, preferably at least about 7, especially at least about 8 orabove. For the homogeneously branched substantially linear ethyleneinterpolymers, the higher the I₁₀/I₂ ratio, the better theprocessability.

[0056] The rheological processing index (PI), onset of surface and grossmelt fracture are measured using a gas extrusion rheometer (GER). TheGER is described by M. Shida, R. N. Shroff and L. V. Cancio in Polym.Eng. Sci., Vol. 17, no. 11, p. 770 (1977), and in Rheometers for MoltenPlastics by John Dealy, published by Van Nostrand Reinhold Co. (1982) onpages 97-99, the disclosures of both of which are incorporated herein byreference. PI testing is performed at a temperature of 190° C., atnitrogen pressure of 2500 psig using 0.0296 inch diameter, 20:1 L/D diehaving an entrance angle of 180°. The GER processing index is calculatedin millipoise units from the following equation:

PI=2.15×10⁶ dynes/cm²/(1000×shear rate),

[0057] where: 2.15×10⁶ dynes/cm² is the shear stress at 2500 psi, andthe shear rate is the shear rate at the wall as represented by thefollowing equation:

32 Q′/(60 sec/min)(0.745)(Diameter×2.54 cm/in)³, where:

[0058] Q′ is the extrusion rate (gms/min),

[0059] 0.745 is the melt density of polyethylene (gm/cm³), and

[0060] Diameter is the orifice diameter of the capillary (inches).

[0061] The PI is the apparent viscosity of a material measured atapparent shear stress of 2.15×10⁶ dyne/cm².

[0062] For the substantially linear ethylene interpolymers used herein,the PI is preferably less than or equal to 70 percent of that of acomparative linear ethylene interpolymer; that is, a homogeneouslybranched linear ethylene interpolymer having about the same I₂ andM_(w)/M_(n).

[0063] An apparent shear stress vs. apparent shear rate plot is used toidentify the melt fracture phenomena. According to Ramamurthy in Journalof Rheology, 30(2), pages 337-357 (1986), above a certain critical flowrate, the observed extrudate irregularities may be broadly classifiedinto two main types: surface melt fracture and gross melt fracture.

[0064] Surface melt fracture occurs under apparently steady flowconditions and ranges in detail from loss of specular gloss to the moresevere form of “sharkskin”. In this disclosure, the onset of surfacemelt fracture is characterized at the beginning of losing extrudategloss at which the surface roughness of extrudate can only be detectedby 40x magnification. The critical shear rate at onset of surface meltfracture for the substantially linear olefin polymers is at least 50percent greater than the critical shear rate at the onset of surfacemelt fracture of a comparative linear ethylene interpolymer; that is, ahomogeneously branched linear ethylene interpolymer having about thesame I₂ and M_(w)/M_(n).

[0065] Gross melt fracture occurs at unsteady flow conditions and rangesin detail from regular (alternating rough and smooth, helical, etc.) torandom distortions. For commercial acceptability, (e.g., in blown filmproducts), surface defects should be minimal, if not absent. Thecritical shear rate at onset of surface melt fracture (OSMF) and onsetof gross melt fracture (OGMF) will be used herein based on the changesof surface roughness and configurations of the extrudates extruded by aGER.

[0066] GER testing for melt fracture determinations is performed at atemperature of 190° C., at nitrogen pressures between 5250 to 500 psigusing a 0.0296 inch diameter, 20:1 L/D die having an entrance angle of180°.

[0067] Substantially linear ethylene interpolymers suitable for useherein are characterized as having:

[0068] (a) a melt flow ratio, I₁₀/I₂≧5.63,

[0069] (b) a molecular weight distribution, M_(w)/M_(n), as determinedby gel permeation chromatography and defined by the equation:

(M_(w)/M_(n))≦(I₁₀/I₂)−4.63,

[0070] (c) a gas extrusion rheology such that the critical shear rate atonset of surface melt fracture for the substantially linear ethyleneinterpolymer is at least 50 percent greater than the critical shear rateat the onset of surface melt fracture for a comparative homogeneouslybranched linear ethylene interpolymer, wherein the substantially linearethylene interpolymer and the homogeneously branched linear ethyleneinterpolymer comprise the same comonomer or comonomers, thehomogeneously branched linear ethylene interpolymer has an I₂ andM_(w)/M_(n) within ten percent of the substantially linear ethyleneinterpolymer and wherein the respective critical shear rates of theinterpolymers are measured at the same melt temperature, under the samenitrogen load using a gas extrusion rheometer, and

[0071] (d) a single differential scanning calorimetry, DSC, melting peakbetween −30° and 150° C.

Molecular Weight Distribution Determination

[0072] The molecular weight distribution of the ethylene interpolymersis analyzed by gel permeation chromatography (GPC) on a Waters 150C hightemperature chromatographic unit equipped with three mixed porositycolumns (Polymer Laboratories 10³, 10⁴, 10⁵, and 10⁶), operating at asystem temperature of 140° C. The solvent is 1,2,4-trichlorobenzene,from which 0.3 percent by weight solutions of the samples are preparedfor injection. The flow rate is 1.0 milliliter/minute and the injectionsize is 200 microliters. A differential refractometer is being used asthe detector.

[0073] The molecular weight determination with respect to the polymerbackbone is deduced by using narrow molecular weight distributionpolystyrene standards (from Polymer Laboratories) in conjunction withtheir elution volumes. The equivalent polyethylene molecular weights aredetermined by using appropriate Mark-Houwink coefficients forpolyethylene and polystyrene (as described by Williams and Ward inJournal of Polymer Science, Polymer Letters, Vol. 6, p. 621, 1968, thedisclosure of which is incorporated herein by reference) to derive thefollowing equation:

M_(polyethylene)=a*(M_(polystyrene))^(b).

[0074] In this equation, a=0.4316 and b=1.0. Weight average molecularweight, M_(w), is calculated in the usual manner according to thefollowing formula: Mj=(Σw_(i)(M_(i) ^(J))^(j); where w_(i) is the weightfraction of the molecules with molecular weight M_(i) eluting from theGPC column in fraction i and j=1 when calculating M_(w) and j=−1 whencalculating M_(n).

[0075] For the homogeneously branched ethylene interpolymers usedherein, the molecular weight distribution (M_(w)/M_(n)) is thought notto be critical but preferably the molecular weight distribution, asdetermined using gel permeation chromatography (GPC), is from about 1.8to about 2.8, more preferably from about 1.89 to about 2.2 andespecially less than 2.

Determination of the Slope of Strain Hardening Coefficient

[0076] The slope of strain hardening is measured by compression moldinga plaque from the polymer to be tested. Typically, the plaque is moldedat about 190° C. for 4 minutes under almost no pressure and then pressedfor 3 minutes under a pressure of about 20,000 psi. The plaque is thenallowed to cool at about 8° C./minute under about 2,000 psi pressure.The molded plaque has a thickness of from about 0.005 to about 0.007inches. The plaque is then cut into a dogbone shaped test piece using asuitable die. A suitable test piece is 0.315 inches wide and 1.063inches long. The start of the curved portion of the dogbone shape beginsat 0.315 inches from each end of the sample and gently curves (i.e.,tapers) to an interior width of from about 0.079 to about 0.090 inches.The curve ends at a point 0.118 inches from the start of the curve suchthat the interior portion of the dogbone test piece has a length of0.197 inches. FIG. 1A and 1B show scale diagrams of suitable testdogbones.

[0077] The tensile properties of the test sample are tested on anInstron Tensile Tester at a crosshead speed of 1 inch/minute. The slopeof strain hardening is calculated from the resulting tensile curve bydrawing a line parallel to the strain hardening region (i.e. a 10percent secant tangent line). The strain hardening region occurs afterthe sample has pulled its initial load (usually with little or noelongation during the initial load) and after the sample has gonethrough a slight drawing stage (usually with little or no increase inload, but with increasing extension (i.e., strain)). In the strainhardening region, the load and the extension of the sample both continueto increase up to the failure point.

[0078]FIG. 2 shows a tensile curve with the various stages of strainhardening as well as the slope of strain hardening. The slope of strainhardening is conveniently taken as the line representing a 10 percentsecant tangent which is calculated from the failure point to the pointat 10 percent extension before the failure point (where 10 percentextension before is equal to 90 percent of the total extension orstrain).

[0079] A more precise methodology for calculating the slope of strainhardening is performing linear regression analysis using the tensilecurve datapoints that represent the last 10 percent extension before thefailure point.

[0080] The slope of strain hardening coefficient (SHC) is calculatedaccording to the equation:

SHC=(slope of strain hardening)*(I ₂))^(0.25)

[0081] where I₂=melt index in grams/10 minutes, as determined inaccordance with ASTM D-1238, Condition 190° C./2.16 kg.

[0082] For the first interpolymer or the second interpolymer or both,preferably the SHC is greater than or equal to 1.3, more preferablygreater than or equal to about 1.5, especially in the range of from 1.3to about 10, and most especially in the range of from about 1.5 to about5. More preferably, the inventive diverse interpolymer compositionitself is characterized as having a SHC greater than or equal to 0.85,most preferably greater than or equal to 0.95, most especially greaterthan or equal to 1.

The Second Ethylene Interpolymer

[0083] The second ethylene interpolymer can be a homogeneously branchedethylene interpolymer or a heterogeneously branched ethyleneinterpolymer. But, preferably, the second interpolymer is aheterogeneously branched (e.g., Ziegler polymerized) interpolymer ofethylene with at least one C₃-C₂₀ α-olefin (e.g., linear low densitypolyethylene (LLDPE)). By the term “heterogeneously branched ethyleneinterpolymer” it is meant the ethylene interpolymer has a SCBDI of lessthan 50 percent.

[0084] Heterogeneously branched ethylene interpolymers differ from thehomogeneously branched ethylene interpolymers primarily in theirbranching distribution. For example, heterogeneously branched LLDPEpolymers have a distribution of branching, including a highly branchedportion (similar to a very low density polyethylene), a medium branchedportion (similar to a medium branched polyethylene) and an essentiallylinear portion (similar to linear homopolymer polyethylene). The amountof each of these fractions varies depending upon the whole polymerproperties desired. For example, linear homopolymer polyethylene hasneither branched nor highly branched fractions, but is linear. A verylow density heterogeneous polyethylene having a density from about 0.9g/cm³ to about 0.915 g/cm³ (such as ATTANE™ copolymers, sold by The DowChemical Company and FLEXOMER® sold by Union Carbide Corporation) has ahigher percentage of the highly short chain branched fraction, thuslowering the density of the whole polymer.

[0085] Heterogeneously branched ethylene interpolymers (such as DOWLEX®LLDPE resins sold by The Dow Chemical Company) have lower amounts of thehighly branched fraction, but has a greater amount of the mediumbranched fraction. While ATREF will show homogeneously branched ethyleneinterpolymers typically are characterized by a single relatively narrowpeak at some elution temperature, heterogeneously branched ethyleneinterpolymers like DOWLEX™ LLDPE 2045 resin have a broad branchingdistribution, as represented by the breadth of elution temperatures overwhich the polymer fractions elute. DOWLEX™ LLDPE 2045 resin also has adistinct peak at an elution temperature of about 98° C., indicating the“linear”, “high density” or “crystalline” polymer fraction of the wholepolymer.

[0086] Preferably, the heterogeneously branched ethylene interpolymer isa copolymer of ethylene with a C₃-C₂₀ α-olefin, wherein, morepreferably, the copolymer has a density from about 0.93 g/cm³ to about0.95 g/cm³, and most preferably a melt index (I₂) from about 0.1 g/10min to about 500 g/10 min. Most especially, the heterogeneously branchedinterpolymer will have a density greater than 0.920 g/cc and especiallygreater than or equal to 0.935 g/cm³.

[0087] In particularly preferred embodiments, the heterogeneouslybranched interpolymer will have a density of no more than 0.95 g/cm³,more preferably no more than about 0.945 g/cm³, and most preferably nomore than about 0.94 g/cm³. When the density of the heterogeneouslybranched interpolymer is no more than about 0.95 g/cm³, the interpolymerwill typically be characterized by a molecular weight distribution(M_(w)/M_(n)) greater than 3, preferably at least 3.2, and morepreferably at least 3.3. Further, when the density of theheterogeneously branched interpolymer is no more than about 0.95 g/cm³,the SCBDI, as defined above, is less than 50 percent and most commonlyless than or equal to 45 percent.

[0088] The heterogeneously branched ethylene interpolymers used hereinalso have at least two melting points, as determined using DifferentialScanning Calorimetry (DSC) between the temperature range of −30° to 150°C.

Manufacturing and Preparation

[0089] The compositions disclosed herein can be formed by any convenientmethod, including dry blending the individual components andsubsequently melt mixing or by pre-melt mixing in a separate extruder(e.g., a Banbury mixer, a Haake mixer, a Brabender internal mixer, or atwin screw extruder).

[0090] Another technique for making the compositions in-situ isdisclosed in pending U.S. Ser. No. 08/010,958, entitled EthyleneInterpolymerizations, which was filed Jan. 29, 1993 in the names ofBrian W. S. Kolthammer and Robert S. Cardwell, the disclosure of whichis incorporated herein in its entirety by reference. U.S. Ser. No.08/010,958 describes, inter alia, interpolymerizations of ethylene andC₃-C₂₀ α-olefins using a homogeneous catalyst in at least one reactorand a heterogeneous catalyst in at least one other reactor. The reactorscan be operated sequentially or in parallel.

[0091] The compositions can also be made by fractionating aheterogeneous ethylene interpolymer into specific polymer fractions witheach fraction having a narrow composition (i.e., branching)distribution, selecting the fraction having the specified properties(e.g., SHC≧1.3), and blending the selected fraction in the appropriateamounts with another ethylene polymer. This method is obviously not aseconomical as the in-situ interpolymerizations of U.S. Ser. No.08/010,958, but nonetheless can be used to obtain the present diverseinterpolymer composition.

Fabricated Articles Made from the Inventive Diverse InterpolymerComposition

[0092] Many useful fabricated articles benefit from the diverseinterpolymer composition disclosed herein. For example, moldingoperations can be used to form useful fabricated articles or parts fromthe compositions disclosed herein, including various injection moldingprocesses (e.g., that described in Modern Plastics Encyclopedia/89, MidOctober 1988 Issue, Volume 65, Number 11, pp. 264-268, “Introduction toInjection Molding” by H. Randall Parker and on pp. 270-271, “InjectionMolding Thermoplastics” by Michael W. Green, the disclosures of whichare incorporated herein by reference) and blow molding processes (e.g.,that described in Modern Plastics Encyclopedia/89, Mid October 1988Issue, Volume 65, Number 11, pp.217-218, “Extrusion-Blow Molding” byChristopher Irwin, the disclosure of which is incorporated herein byreference), profile extrusion, calendering, pultrusion (e.g., pipes) andcombinations thereof. Rotomolded articles can also benefit from thenovel compositions described herein. Rotomolding techniques are wellknown to those skilled in the art and include, for example, thosedescribed in Modern Plastics Encyclopedia/89, Mid October 1988 Issue,Volume 65, Number 11, pp.296-301, “Rotational Molding” by R. L. Fair,the disclosure of which is incorporated herein by reference).

[0093] Fibers (e.g., staple fibers, melt blown fibers or spunbondedfibers (using, e.g., systems as disclosed in U.S. Pat. No. 4,340,563;U.S. Pat. No. 4,663,220; U.S. Pat. No. 4,668,566; or U.S. Pat. No.4,322,027, all of which are incorporated herein by reference), and gelspun fibers (e.g., the system disclosed in U.S. Pat. No. 4,413,110,incorporated herein by reference)), both woven and nonwoven fabrics(e.g., spunlaced fabrics disclosed in U.S. Pat. No. 3,485,706,incorporated herein by reference) or structures made from such fibers(including, e.g., blends of these fibers with other fibers, e.g., PET orcotton)) can also be made from the inventive diverse compositiondisclosed herein. Elastic fibers comprising the inventive diverseinterpolymer composition is a particularly preferred use.

[0094] Coatings, films and film structures (especially biaxial shrinkfilms, lamination films and other films and film applications thatrequire excellent toughness properties) particularly benefit from theinventive interpolymers compositions described herein. Such coatings,films and film structures can be made using conventional hot blown filmfabrication techniques, cast extrusion, extrusion coating, coextrusiontechniques, and biaxial orientation processes such as tenter frames ordouble bubble processes.

[0095] Conventional hot blown film processes are described, for example,in The Encyclopedia of Chemical Technology, Kirk-Othmer, Third Edition,John Wiley & Sons, New York, 1981, Vol. 16, pp.416-417 and Vol.18,pp.191-192, the disclosures of which are incorporated herein byreference. Biaxial orientation film manufacturing processes (forexample, a “double bubble” process or a “trapped bubble” process) usefulfabricate shrink film from the inventive composition are described inU.S. Pat. No. 3,456,044 (Pahlke), U.S. Pat. No. 4,352,849 (Mueller),U.S. Pat. No. 4,597,920 (Golike), U.S. Pat. No. 4,820,557 (Warren), U.S.Pat. No. 4,837,084 (Warren), U.S. Pat. No. 4,865,902 (Golike et al.),U.S. Pat. No. 4,927,708 (Herran et al.), U.S. Pat. No.4,952,451(Mueller), U.S. Pat. No. 4,963,419 (Lustig et al.), and U.S. Pat. No.5,059,481 (Lustig et al.), the disclosures of each of which areincorporated herein by reference, can also be used to make filmstructures from the inventive diverse interpolymer composition describedherein. The film structures can also be made using the tenter-frametechnique, such as that conventionally used for oriented polypropylene.

[0096] Other multi-layer film manufacturing techniques for foodpackaging applications for which the present inventive composition iswell suited are described in Packaging Foods With Plastics, by Wilmer A.Jenkins and James P. Harrington (1991), pp.19-27, and in “CoextrusionBasics” by Thomas I. Butler, Film Extrusion Manual: Process, Materials,Properties pp. 31-80 (published by TAPPI Press (1992)) the disclosuresof which are incorporated herein by reference. The films may bemonolayer or multilayer films. The film made from the inventiveinterpolymer compositions can also be coextruded with the other layer(s)or the film can be laminated onto another layer(s) in a secondaryoperation, such as that described in Packaging Foods With Plastics, byWilmer A. Jenkins and James P. Harrington (1991) or that described in“Coextrusion For Barrier Packaging” by W. J. Schrenk and C. R. Finch,Society of Plastics Engineers RETEC Proceedings, Jun. 15-17 (1981), pp.211-229, the disclosure of which is incorporated herein by reference. Ifa monolayer film is produced via tubular film (i.e., blown filmtechniques) or flat die (i.e., cast film) as described by K. R. Osbornand W. A. Jenkins in “Plastic Films, Technology and PackagingApplications” (Technomic Publishing Co., Inc. (1992)), the disclosure ofwhich is incorporated herein by reference, then the film must go throughan additional post-extrusion step of adhesive or extrusion lamination toother packaging material layers to form a multilayer structure. If thefilm is a coextrusion of two or more layers (also described by Osbornand Jenkins), the film may still be laminated to additional layers ofpackaging materials, depending on the other physical requirements of thefinal film. “Laminations Vs. Coextrusion” by D. Dumbleton, ConvertingMagazine (September 1992), the disclosure of which is incorporatedherein by reference, also discusses lamination versus coextrusion.Monolayer and coextruded films can also go through other post extrusiontechniques, such as a biaxial orientation process.

[0097] Other film applications that can use the inventive diverseinterpolymer composition include pouches (especially via verticalform-fill-seal equipment), bags, sacks (for example, heavy-duty shippingsacks), stretch film (especially, stretch cling films), liners, diaperbacksheets, tarps and canvases, bubble wrap, skin packaging films,blister packaging films and laminated films (for example, TYVEK film anddecorative film).

[0098] Extrusion coating is yet another technique for producingmultilayer structures using the inventive diverse interpolymercomposition described herein. The inventive composition can comprise atleast one layer of the structure. Similar to cast film, extrusioncoating is a flat die technique. For example, a sealant layer (which theinventive interpolymer composition is also useful for) can be extrusioncoated onto a substrate either in the form of a monolayer or acoextruded extrudate.

[0099] Generally, for a multilayer film or packaging structure, theinventive diverse interpolymer composition described herein comprises atleast one layer of the total multilayer structure. Other layers of themultilayer structure include but are not limited to barrier layers,and/or tie layers, and/or structural layers. Various materials can beused for these layers, with some of them being used as more than onelayer in the same film structure. Some of these materials include: foil,nylon, ethylene/vinyl alcohol (EVOH) copolymers, polyvinylidene chloride(PVdC), polyethylene terephthalate (PET), oriented polypropylene (OPP),ethylene/vinyl acetate (EVA) copolymers, ethylene/acrylic acid (EAA)copolymers, ethylene/methacrylic acid (EMAA) copolymers, LLDPE, HDPE,LDPE, nylon, graft adhesive polymers (for example., maleic anhydridegrafted polyethylene), and paper. Generally, the multilayer filmstructures comprise from 2 to about 7 layers. Additives such asantioxidants (e.g., hindered phenolics (e.g., Irganox® 1010 made by CibaGeigy Corp.), phosphites (e.g., Irgafos® 168 also made by Ciba GeigyCorp.)), cling additives (e.g., PIB), antiblock additives, slip agents,pigments, fillers, or combinations thereof, can be included in theformulations, to the extent that they do not interfere with the enhancedformulation properties discovered by Applicants.

EXAMPLE 1

[0100] In an evaluation to provide polymer blends with excellenttoughness properties, several different ethylene interpolymers wereobtained. These interpolymers all had relatively low I₂ melt indexes butthey varied as to homogeneity, comonomer type, and density. Table 1lists the various ethylene polymers used in the evaluation. TABLE 1Interpolymer I₂, Melt Density, Comonomer Resin Type Index g/cc Type A389-S homogeneously 0.82 0.871 1-butene branched B 389-F homogeneously0.97 0.869 1-octene branched C DOWLEX heterogeneously 1.0 0.920 1-octene2045 branched D DOWLEX heterogeneously 2.4 0.934 1-octene 2037 branchedE AFFINITY homogeneously 0.97 0.909 1-octene PL1840 branched F DOWLEXheterogeneously 0.93 0.935 1-octene 2038 branched G SCLAIRheterogeneously 1.66 0.936 1-butene 14B branched

[0101] The ethylene interpolymers were tumble dry blended at variousweight percents and extruded at about 200° C. on a 15 mm co-rotatingtwin-screw extruder to provide several two component polymer blends. Theindividual interpolymers and the interpolymer polymer blends werecompression molded and tested to determine their respective intrinsictear performance. Also, Resin B, Resin E and Resin F were tested usingdogbones according to FIG. 1A to determine their respective slope ofstrain hardening coefficient. Table 2 provides the designation of thesingle polymer compositions, the description of the polymer blends andresultant properties for both.

[0102] From the data in Table 2, FIG. 3-9 were generated. FIG. 3 showsthe relationship between intrinsic tear (in grams) and the slope ofstrain hardening coefficient (SHC) for two heterogeneously branchedethylene/1-octene. TABLE 2 Overall Intrinsic Yield Ultimate UltimateEnergy Energy Density, Tear, Yield Stress, Stress Stress, Stress atBreak, at Break Example Composition g/cm³ gm-force SHC psi STD, psi psiSTD, psi psi STD, psi Inv. Ex 1 25% Resin E + 75% Resin G 0.9303 154.5ND 2,289 52 3,288 255 341 27 Comp Run 1* 25% Resin E + 75% Resin F0.9288 271.2 ND 2,284 33 4,485 200 407 30 Inv. Ex 2 50% Resin E + 50%Resin G 0.9233 264.1 ND 1,824 37 3,999 145 385 19 Comp Run 2* 50% ResinE + 50% Resin F 0.9230 350.4 ND 1,770 30 3,958 426 328 46 Inv. Ex 3 25%Resin A + 75% Resin D 0.9206 229.4 ND 1,752 15 3,541 229 346 27 Comp Run3* 25% Resin B + 75% Resin D 0.9181 227.0 ND 1,702 52 3,481 172 325 26Comp Run 4* 45% Resin A + 55% Resin C 0.8992 172.6 ND 683 32 2,774 274215 29 Comp Run 5* 45% Resin B + 55% Resin C 0.8964 281.2 ND 708 242,623 156 217 16 Comp Run 6* 100% Resin A 0.8714 14.8 ND 139 3 1,463 99121 11 Comp Run 7* 100% Resin B 0.8688 35.9 ND 131 7 1,479 78 105 6 CompRun 8* 100% Resin C 0.920 405.6 1.5 1,637 38 3,813 116 307 13 Comp Run9* 100% Resin D 0.934 125.7 ND 2,735 69 4,043 167 382 20 Comp Run 10100% Resin E 0.909 410.7 2.1 1,030 21 3,882 208 289 23 Comp Run 11* 100%Resin F 0.935 124.9 0.55 2,781 49 4,335 558 406 67 Comp Run 12 100%Resin G 0.936 60.0 ND 2,566 63 2,327 80 200 11

[0103] copolymers (Resin C and Resin F) and one homogeneously branchedethylene/1-octene copolymer (Resin E). While this figure was generatedusing single or component interpolymers (and without being held to anyparticular theory), we believe FIG. 3 is also applicable to polymerblends, especially those polymer blends that are not characterized bysynergistic toughness properties.

[0104]FIG. 4 shows the relationship between intrinsic tear (in grams)and the overall density (in grams per cubic centimeter) for varioussingle polymer and polymer blend compositions, including inventiveinterpolymer combinations (Inventive Example 1, Inventive Example 2 andInventive Example 3). FIG. 4 shows Inventive Example 1 (which had anintrinsic tear of 229.4 grams) exhibited toughness that approximated the“mixing rule” response. That is, the intrinsic tear of Inventive Example1 was within 29 percent of the value calculable from correspondingcomponent interpolymers.

[0105] Similarly, FIG. 4 shows Inventive Example 2 (which had anintrinsic tear of 264.1 grams) exhibited toughness that approximated the“mixing rule”. The intrinsic tear of Inventive Example 2 was within 33percent of that predictable based on fractional weight averagecalculations using corresponding interpolymers. Inventive Example 2 wasalso within 33 percent of the intrinsic tear performance of a polymerblend made of two interpolymers, each comprised of the same comonomer(comparative run 2).

[0106]FIG. 4 also shows Inventive Example 3 (which had an intrinsic tearof 229.4 grams) exhibited toughness that was equivalent to that of apolymer blend made of two interpolymers, each comprised of the samecomonomer (comparative run 3).

[0107] The results for Inventive Example 1, Inventive Example 2 andInventive Example. 3 was a surprising unexpected result because thesedual interpolymer blends all comprises one ethylene interpolymer whichis comprised of a lower α-olefin while the “mixing rule” comparison inFIG. 4 consists of a higher α-olefin single polymer and the polymerblend comparisons set forth in FIG. 4 consist of two higher α-olefininterpolymers and higher α-olefin interpolymers can well known toexhibit improved toughness relative to lower α-olefin interpolymers. Thefact that comparable or equivalent toughness can be accomplished usingcombinations with a lower α-olefin is extremely surprising andunexpected.

[0108]FIG. 5 and FIG. 6 show that the intrinsic tear performance ofInventive Example 3 is substantially higher that predictable accordingto the “mixing rule” and equivalent to a same-comonomer polymer blend(comparative run 3).

[0109]FIG. 7 and FIG. 8 show that the intrinsic tear performance ofInventive Example 1 and Inventive Example 2 are substantially comparableto that predictable by the “mixing rule”.

[0110]FIG. 9 shows that at an overall composition density of 0.8992g/cm³, a polymer blend comprised of two interpolymers, each having adifferent comonomer (comparative run 4) does not result in a finalcombination that exhibits good toughness. The intrinsic tear ofcomparative run 4 is substantially lower than that predicted by the“mixing rule” and substantially lower than that of a polymer blendcomprised of two interpolymers, each comprising a higher α-olefincomonomer (comparative run 5).

We claim:
 1. A diverse interpolymer composition comprising (A) fromabout 5 percent (by weight of the total composition) to about 95 percent(by weight of the total composition) of at least one first ethyleneinterpolymer, and (B) from about 95 percent (by weight of the totalcomposition) to about 5 percent (by weight of the total composition) ofat least one second ethylene interpolymer; wherein the firstinterpolymer is characterized as comprising a different comonomerrelative to the second interpolymer; wherein one interpolymer is ahomogeneously branched ethylene interpolymer and the other interpolymeris a heterogeneously branched ethylene interpolymer or a homogeneouslybranched ethylene interpolymer, and wherein the composition ischaracterized as having a density greater than or equal to 0.90 g/cm³.2. The composition according to claim 1 wherein the first interpolymeris a homogeneously branched linear ethylene interpolymer.
 3. Thecomposition according to claim 2 wherein the homogeneously branchedethylene interpolymer has a slope of strain hardening coefficientgreater than or equal to about 1.3.
 4. The composition according toclaim 1 wherein the second interpolymer is heterogeneously branchedethylene interpolymer.
 5. The composition according to claim 4 whereinthe heterogeneously branched ethylene interpolymer is a heterogeneouslybranched linear ethylene interpolymer.
 6. The composition according toclaim 1 wherein the first interpolymer is a substantially linearethylene interpolymer characterized as having: (a) a melt flow ratio,I₁₀/I₂≧5.63, (b) a molecular weight distribution, M_(w)/M_(n), asdetermined by gel permeation chromatography and defined by the equation:(M_(w)/M_(n))≦(I₁₀/I₂)−4.63, (c) a gas extrusion rheology such that thecritical shear rate at onset of surface melt fracture for thesubstantially linear ethylene interpolymer is at least 50 percentgreater than the critical shear rate at the onset of surface meltfracture for a comparative homogeneously branched linear ethyleneinterpolymer, wherein the substantially linear ethylene interpolymer andthe homogeneously branched linear ethylene interpolymer comprise thesame comonomer or comonomers, the homogeneously branched linear ethyleneinterpolymer has an I₂ and M_(w)/M_(n) within ten percent of thesubstantially linear ethylene interpolymer and wherein the respectivecritical shear rates of the interpolymers are measured at the same melttemperature, under the same nitrogen load using a gas extrusionrheometer, and (d) a single differential scanning calorimetry, DSC,melting peak between −30° and 150° C.
 7. The composition according toclaim 1 wherein the first interpolymer is a homogeneously branchedlinear ethylene/α-olefin copolymer.
 8. The composition according toclaim 1 wherein the first interpolymer is a substantially linearethylene/α-olefin copolymer.
 9. The composition according to claim 1wherein the second interpolymer is a heterogeneously branchedethylene/α-olefin copolymer.
 10. The composition according to claim 1wherein the first interpolymer or second interpolymer is a copolymer ofethylene and 1-octene and the other interpolymer is a copolymer ofethylene and 1-pentene.
 11. The composition according to claim 1 whereinthe first interpolymer or second interpolymer is a copolymer of ethyleneand 1-octene and the other interpolymer is a copolymer of ethylene and1-butene.
 12. The composition according to claim 1 wherein the firstinterpolymer or second interpolymer is a copolymer of ethylene and1-octene and the other interpolymer is a copolymer of ethylene and1-hexene.
 13. The composition according to claim 1 wherein the firstinterpolymer or second interpolymer is a copolymer of ethylene and1-octene and the other interpolymer is a copolymer of ethylene and1-heptene.
 14. The composition according to claim 1 wherein thecomposition is further characterized as having an intrinsic tear valuegreater than or equal to 150 grams, as determined in accordance withASTM D-1922, Method A.
 15. The composition according to claim 1 whereinthe composition is further characterized as having an intrinsic tearvalue greater than or equal to 200 grams, as determined in accordancewith ASTM D-1922, Method A.
 16. The composition according to claim 1wherein the composition is further characterized as having a slope ofstrain hardening coefficient (SHC) greater than or equal to 0.85. 17.The composition according to claim 1 wherein the composition is furthercharacterized as having a slope of strain hardening coefficient (SHC)greater than or equal to 0.95.
 18. A diverse interpolymer compositioncomprising (A) from about 5 percent (by weight of the total composition)to about 95 percent (by weight of the total composition) of at least onefirst ethylene interpolymer, and (B) from about 95 percent (by weight ofthe total composition) to about 5 percent (by weight of the totalcomposition) of at least one second ethylene interpolymer; wherein thefirst interpolymer is characterized as comprising a different comonomerrelative to the second interpolymer and as having a lower densityrelative to the second interpolymer; the second interpolymer ischaracterized as having a density less than or equal to 0.95 g/cm³;wherein one interpolymer is a homogeneously branched ethyleneinterpolymer and the other interpolymer is a heterogeneously branchedethylene interpolymer or a homogeneously branched ethylene interpolymer;and wherein the composition is characterized as having a density in therange of from greater than or equal to 0.90 g/cc to about 0.935 g/cc.19. A film comprising the composition of claim
 1. 20. A fiber comprisingthe composition of claim
 1. 21. A molding comprising the composition ofclaim
 1. 22. A coating comprising the composition of claim
 1. 23. Aprofile comprising the composition of claim
 1. 24. A pouch comprisingthe composition of claim
 1. 25. A sealant film layer comprising thecomposition of claim
 1. 26. A carpet backing comprising the compositionof claim
 1. 27. A liner comprising the composition of claim
 1. 28. Ashrink film comprising the composition of claim
 1. 29. A stretch filmcomprising the composition of claim
 1. 30. An extrusion coatingcomprising the composition of claim
 1. 31. A laminating film comprisingthe composition of claim
 1. 32. A rotomolding comprising the compositionof claim
 1. 33. A sack comprising the composition of claim
 1. 34. Thesack according to claim 33 wherein the sack is a grocery sack.
 35. A bagcomprising the composition of claim
 1. 36. The bag according to claim 35wherein the bag is a merchandise bag.
 37. The pouch according to claim24 wherein the pouch is fabricated using form-fill-seal (FFS) equipment.38. The pouch according to claim 37 wherein the equipment is a verticalform-fill-seal unit.